Serious Error in 2018 ARRL Handbook!

In the 2018 Handbook, on page 11-3, second column, an equation is given for an AM signal with fC carrier and fM modulating signal. It's the sum of three expressions, one for the carrier, one for the upper sideband, and the third for the lower sideband, as explained in the text that follows.

But the sine functions for both sidebands are shown as the same: 2π(fC + fM)